Alcoholysis of lower fatty acid groups in polyhydroxy fatty esters



Patented Feb. 16, 1954 UITED STATES PATENT OFFICE ALCOI'IOLYSIS OF LOWER FATTY ACID GROUPS IN POLYHYDROXY FATTY ESTERS Roger L. Logan, Elkins Park, Pa., assignor to Kessler Chemical C0,, Inc., Philadelphia, Pa, a corporation of Pennsylvania No Drawing. Application November 22, 1954 Serial No. 197,180

9 Claims.

by alkaline saponification, followedv by acid hy- 1 drolysis or by high pressure hydrolysis with water.

Unfortunately, in the case of esters, the removal of the lower fatty acid groups by these methods results in the removal of the terminal alcohol group. It is, therefore, necessary to reesterify, which is a long and expensive process. Thus, for example, it is well known to treat an ester of oleic acid with performic acid to form a mixture of esters of 9-formoxy-l0-hydroxy stearate and l0-iormoxy-9-hydroxy stearate. Alkaline saponification followed by acid hydrolysis readily removes the formoxy groups, but also removes the terminal alcohol group. Thus, it is necessary to re-esterify to replace the terminal alcohol group.

An unexpected advantage of this invention is that it permits the formation of esters of polyhydroxy fatty acids with long chain alcohols or glycols without the danger of interesterification U which is present when the heretofore used methods of reacting a long chain alcohol orglycols with polyhydroxy fatty acids are used. As a result of the method of this invention, it is possible to react a long chain alcohol with an unsaturated fatty acid and then hydroxylate with, for example, performic or peracetic acid to form the formoxy or acetoxy compounds. The method of this invention provides for the removal of they formoxy or acetoxy groups without removing or substituting the terminal alcohol group. Obviously, by this method a much purer product can be achieved since there is no chance for the glycol groups in the polyhydroxy acid to react with terminal acid groups.

The broad object of this invention is, therefore, to remove lower fatty acid groups from esters of polyhydroxy fatty acids without removing or replacing the terminal alcohol group.

Broadly speaking, the method in accordance with this invention comprises reacting an ester of a polyhydroxy fatty acid esterified by an alcohol at the terminal group and esterified at a hydroxyl group with a fatty acid group, with an alcohol and distilling as the ester formed with the lower fatty acid group. The reaction is illustrated by the following specific example:

Preferably, carrying out the method in accordance with this invention, dry alcohol is added to a hydroxylated ester of a fatty acid so that the boiling point of the mixture is maintained between 60 C. and 150 C. As the newly formed ester distills off, more alcohol is added. The reaction starts readily if all of the ingredients are dry and proceeds to completion. Any standard distillation unit with a fractionating column of sufficient efficiency to separate the ester formed from the alcohol used, may be utilized.

It is preferred to use a small amount of catalyst such as alkali metals, their alcoholates, oxides or hydroxides, such as sodium hydroxide, potassium hydroxide, barium hydroxide, sodium metal, etc. ,Acid catalysts such as sulfuric acid and su'lfonic acids may be used. The catalysts may be used by dissolving them in the alcohol and adding the solution to the reaction. The re action will proceed well without catalyst if all ingredients are dry.

The reaction may be run advantageously un der pressure. Pressure increases the boiling points of the reactants and products and thus increases the reaction rate. It allows the presence of greater amounts of alcohol at higher temperatures, and aids in condensing lower esters formed.

By way of more specific example, the method in accordance with this invention can be carried out with an ester of a po-lyhydroxy fatty acid containing lower fatty acid groups such as, for example, an ester in which the terminal ester group may be any alcohol, as, for example, methanol, butanol, propanol, stearyl alcohol, oleyl alcohol or an cctyl alcohol such as 2-ethyl hexanol, and glycols, such as glycerol and polyethylene glycols. The lower fatty acid group may have from 1 to 5 carbon atoms, as, for example, formic, acetic, propionic, butyric or valeric acids. The fatty acid portion of the compound may have from 11 to 22 carbon atoms as, for example,

10,11 dihydroxy undecanoic acid, 9,10 dihydroxy stearic acid, tetrahydroxy stearic acid, trihydroxy stearic acid and 13,14 dihydroxy behenic acid.

The following. specific. examples willbe further illustrative. of, the method accordance. with this invention:

Erample 1 975 grams of a 50% mixture of. methyl formoxy stearate's and methyl esters of Cw and Cw fatty acids having a saponification number of 277, were heated in a distillation apparatua, equipped with a fractionating' column. There. was then then added '70 grams of 99.7% meth anol in which was dissolved 2 grams of sodium hydroxide pellets. The mixture boiled at about 90 C. and methyl format-e formed almost immediately. The first methyl formate distilled; at 38 C.; within a few minutes the vapor temperature dropped to; 33 C; Most. ofthemethylformate distilled. oil. by: the'end; oi five; hours of reaction. Sufiicient methanol was maintained in the distillation pot to keep the temperature at from 135 to 145 C. toward the end of reaction, small amounts being added from time to time.

The tem-perature'at thetop-of the fractionating. column finally rose to 64 C. and stayed at this point under both reflux and distillation. The saponification number of the: resulting mixed methyl. esters was. 192.

Example 2 900gramsof a 50 mixture of methyl'formoxy stearates and methyl ester'of C16' and Gig-fatty acids were heated in a distillation apparatus. There was then added 70'- grams of 99.7 74 methanol. The mixture boiled at about 90 C. Methyl formats formed and distilled in a few minutes after boilingstarted. Methanol was added'slow- 1y from time to time, and methyl formate continued to distill off Thetemperature at the topof thefractionating column rose to 64 C. and remained at 64 C.

under both reflux and distillation. At this point the. reaction was considered complete; The sa'ponification number dropped from approximately- 280 to 18815. The-terminal methyl group was not afiected. The reaction went well inthe absence of catalyst.

Etcampl'e 3 To 200 grams of methyl formoxy undecanoate;

saponification. number. 381-, there.- was added. 40

Examplev 4:

To 800 grams of a mixture of butyl formoxy stearateand butyl stearate; sap-unification number 250, there was added 100 grams ofj'drymetha- 1101 and .8' gram of alkane sulfonic acid. Reaction-tookplace ina 2000 ml. flask equippedwith; 5 30 cm; fractionating column". As soon as the iii 4 reaction temperature in the flask reached 75 0.. methyl formate distilled out of the fractionatlng column at a temperature of 35 C.

At the end of two hours of reaction, the temperature began to rise at the top ofthe fractionating column to theboiling point or methanol. The reaction was completed at the end of three hours. The saponification number dropped from 250 to 171. The removal of formoxy groups was complete.

Example 5 To 800 grams of butyl formoxy stearate, saponificationnumber 250, there was added grams of nebutanol' and 1 gram of alkane sulfonic acid. The reaction took place in a 2000 ml. flask equipped: with. a. 31) cm. fractionating column. Thezreaction began as soon as the distillation flask temperature reached 120 C.

Butyl formate was distilled oil at the top of the fractionating column. The final reaction temperature was C: The reaction time was 5 hours. At the end of that time, the saponiflca tion number of the ester had dropped from 250 to 169, indicating that the removal of formoxy compounds was complete:

Example. 6.

200 grams of commercial glyceryl moncoleate' was hydroxylated" with f ormic: acid and hydrogen peroxide. The-formed glycerylzformoxy hydroxy esters, saponificatiorr number 320, were subjected to the method of this invention.

The. glyceryl formoxy hydroxy esters were heated. with- 60 grams' of methanol containing .25 gram of allianelsulfonic' acid, irn a'500 ml; flash to which had:.been attached. a 30 cm. fractionat ingcolumn.

Methyliformate distilled as soonasthepot'temperature reached 75C.. The temperature at-the top of the. column was36 C; for twohoursofre action.

The temperatureat'the top ofthecolumn rose; durin the-next hour; to 64 C. The final pot" temperature: was 98 C: The reaction: was complated in 3hours. Thefinal sa-ponificatiorr num her was 173.

There. was no evidence of removal or' replacement of. the-terminal glyceryl group.

Example; 7

To 3501 grams of methylformoxy dihydroxy stearate, sa-pon-ifi'cation number 300, there was added: 100 grams: of dry methanol and .7 gram of alkanesulfonicacid. The mixture was heated in a. 500 ml. flask; equipped with a 30' cm. frac ti'onating' column;

Reaction started" when the pot: temperature reached 60 (3'. Methyl formate distilled off at theztopof thecolumn: at-36 C. Thetemperature at the= top of the column started to rise after one hour and live minutes of reactionand the reac tion was: completed in three hours and fifteen minutes. The final pot'temperature' was 92 C! The final product'was agood grade of methyl trihydroxy stearate and had a saponi'flcatibtr number of 17-1.

Example 10(1 gramsofl methanol. wasadded to: 25.0 grams of. methyl formoxy hydroxy stearatawith. a. saponification number. oi 263 and; 4%. free: acid as stearic. 1% H2504 was. added asacata-hzst. A 500 ml. fiaskwas. used. as a. distillation pct ends. 30 cm. fractionating column wasconnectedtothe' pot. The reaction began when. the distillation pot temperature reached 64 C. The top temperature was 33 0. when the methyl formate started to distill. At the end of 2 /2 hours most of the theoretical methyl formate had been collected and the per cent. acid as stearic of the material in the distillation pot had dropped to 1.8. The reaction was completed in 5 hours and the per cent. acid in the distillation pot had dropped to .85. The final saponification number was 187.

What is claimed is:

1. The method which comprises heating a polyhydroxy fatty acid of from 11 to 22 carbon atoms esterified by an aliphatic alcohol at the terminal group and esterified at a hydroxyl group with a lower fatty acid having from 1 to 5 carbon atoms, reacting the thus heated ester with a lower aliphatic alcohol in order to replace the lower fatty acid radical with a hydrogen atom without disturbing the terminal group.

2. The method which comprises heating a polyhydroxy fatty acid of from 11 to 22 carbon atoms esterified by an aliphatic alcohol at the terminal group and esterified at a hydroxyl group with a lower fatty acid having from 1 to 5 carbon atoms, reacting the thus heated ester with a lower aliphatic alcohol in order to replace the lower fatty acid radical with a hydrogen atom without disturbing the terminal group and dis- 1 tilling off the formed ester.

3. The method which comprises heating a polyhydroxy fatty acid of from 11 to 22 carbon atoms esterified by an aliphatic alcohol at the terminal group and esterified at a hydroxyl group with a lower fatty acid having from 1 to 5 carbon atoms, reacting the thus heated ester with a lower aliphatic alcohol in the presence of a catalyst in order to replace the lower fatty radical with a. hydrogen atom without disturbing the terminal group.

4. The method which comprises heating a polyhydroxy fatty acid of from 11 to 22 carbon atoms esterified by an aliphatic alcohol at the terminal group and esterified at a hydroxyl group with a lower fatty acid having from 1 to 5 carbon 6 atoms, reacting the thus heated ester with a lower aliphatic alcohol while maintaining the boiling point of the resulting mixture between and C. in order to replace the lower fatty acid radical with a hydrogen atom without disturbing the terminal group.

5. The method in accordance with claim 1, characterized in that the esterified polyhydroxy fatty acid is methyl formoxy dihydroxy stearate.

6. The method in accordance with claim 1, characterized in that the esterified polyhydroxy fatty acid is methyl formoxy hydroxy stearate.

7. The method which comprises heating dihydroxy stearic acid esterified by methyl alcohol at the terminal group and esterified at a hydroxyl group with formic acid, reacting the thus heated ester with a lower aliphatic alcohol in order to replace the lower fatty acid radical with a hydrogen atom without disturbing the terminal group.

8. The method which comprises heating dihydroxy undecanoic acid esterified by methyl alcohol at the terminal group and esterified at a hydroxyl group with formic acid, reacting the thus heated ester with a lower aliphatic alcohol in order to replace the lower fatty acid radical with a hydrogen atom without disturbing the terminal group.

9. The method which comprises heating dihydroxy stearic acid esterified by butyl alcohol at the terminal group and esterified at a hydroxyl group with stearic acid, reacting the thus heated ester with a lower aliphatic alcohol in order to replace the lower fatty acid radical with a hydrogen atom without disturbing the terminal group.

ROGER L. LOGAN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,360,844 Bradshaw et al Oct. 24, 1944 2,443,280 Swern June 15, 1948 

1. THE METHOD WHICH COMPRISES HEATING A POLYHYDROXY FATTY ACID OF FROM 11 TO 22 CARBON ATOMS ESTERIFIED BY AN ALIPHATIC ALCOHOL AT THE TERMINAL GROUP AND ESTERIFIED AT A HYDROXYL GROUP WITH A LOWER FATTY ACID HAVING FROM 1 TO 5 CARBON ATOMS, REACTING THE THUS HEATED ESTER WITH A LOWER ALIPHATIC ALCOHOL IN ORDER TO REPLACE THE LOWER FATTY ACID RADICAL WITH A HYDROGEN ATOM WITHOUT DISTURBING THE TERMINAL GROUP. 